Serum Peptidome Based Biomarkers Searching for Monitoring Minimal Residual Disease in Adult Acute Monocytic Leukemia

Background: Acute monocytic leukemia (M5) is one common type in acute myeloid leukemia (AML). The present study found that a few M5 had special reproducible chromosomal abnormalities and molecular abnormalities. The heterogeneity and complexity of M5 lead to lack of specific tumor-associated markers for molecular diagnosis and targeted therapy. CLINPROT system, with unique advantages, is a firenew and distinctive proteomics technology and has been widely used in the researches of solid tumor and hemopathic malignancies. This study was to screen a panel of serum peptides associated with M5 different disease states for molecular diagnosis and monitoring minimal residual disease.

Methods: 92 M5 were enrolled for the study from those who were newly diagnosed (ND) in the Second Affiliated Hospital of Xi'an Jiao Tong University from January 2009 to July 2014. The median age was 45 years old (range 18-73) and 57.6% were male. Diagnosis was made according to bone marrow cell morphology, cytochemical staining and cellular immune phenotype. 90 healthy cases (HC) (age range 19-70, median age 43 years old, male/female 51/39) were recruited from those who came to our hospital to undergo healthy physical examination and had no any abnormal symptoms and results. Sera of 92 M5 were gained pre- and post-treatment of chemotherapy. Weak cation exchange magnetic bead combined with matrix assisted laser desorption/ ionization time of flight mass spectrometry were used to compare and analyze serum peptidome of M5 with different disease states. Spearman method was used to do correlation analysis of two variables. Statistical significance was defined as p<0.05.

Results: A total of 42 peptides in the molecular weight range of 700-10000 Da were detected using ClinProt system and statistically different between adult M5 and healthy controls. Among them, 9 peptides were elevated and 33 were decreased in M5. Genetic algorithm (GA) was used to obtain a diagnostic model consisting of 6 peptides that could discriminate M5 from controls with a high sensitivity (100%) and specificity (96.67%). Mass charge ratios (m/z) were 6041.91, 4662.15, 7823.02, 9210.97, 1108.91 and 3263.37 respectively. Blind test verified that this model correctly identified 60 cases out of total 62 M5 and 57 cases from 60 healthy controls. The relative intensities of peptides with m/z of 6041.91 and 4662.15 were increased in the ND group and non-complete remission (CR) group, when comparing with the CR group and HC group(p=0.002; p<0.001), but there was no significant difference between the two groups for any of the peptides (p=0.27, p=0.31). No significant difference was found between the CR group and HC group (p=0.22, p=0.41). The relative intensities of peptides with m/z of 7823.02, 9210.97, 1108.91 and 3263.37 were reduced in the ND group and non-CR group when comparing with the CR group and HC group (p<0.001, p=0.0023, p=0.004, p<0.001), and the two groups had no significant difference (p=0.26, p=0.09, p=0.32, p=0.61). No significant difference was observed between the HC group and CR group (p=0.52, p=0.35, p=0.17, p=0.73). Spearman correlation analysis showed that relative intensities of peptides with m/z of 4662.15, 7823.02 and 9210.97 were correlated with high white blood cells (r=0.88, p<0.001; r=-0.89, p<0.001; p=-0.87, p<0.001), FLT3 mutation (r=0.90, p<0.001; r=-0.87, p<0.001; r=-0.88, p<0.001) , extramedullary disease (r=0.80, p<0.001; r=-0.86, p<0.001; r=- 0.82, p<0.001). The relative intensities of the other three peptides had weak correlation with the unfavorable clinical features of M5 at diagnosis.

Conclusion: This panel of peptides has encouraging efficiency in discriminating M5 from HCs and potential value in monitoring M5 minimal residual disease.